This invention relates to engines and more particular it relates to a breather cap for crankcases, manifolds, valve covers and the like to permit air flow through a filter element between atmosphere and the space within the crankcase or the like. The invention includes the method of manufacturing such a cap. Alternatively, the invention lends itself to incorporation with pollution control devices and the like. Still more particularly, the invention includes the combination of a breather cap of the character described with twist-in locking fingers common in other areas, such as fuel tank caps and the like.
The term "breather cap" as used in the specification and claims herein shall be understood to mean a filter element through which air flow is directed between two or more spaces, as for example in the environments described immediately above. The term "crankcase" shall likewise include all such spaces with which the invention cap may be used.
The invention method permits the making of a plated breather cap. Heretofore, it was difficult to plate breather caps because of problems related to the sealing means. The invention avoids these problems and can easily produce a plated product having all of the other advantages of the invention cap.
Heretofore, many crankcase breather caps have been of the so called "push-in" variety. These depend on simple spring fingers which cooperate with some part of the engine or valve cover or the like to hold the cap in place. This is undesirable for many reasons, including that the springs can loosen, they can form a less than air-tight seal, and the springs often have sharp edges which can injure users handling them.
Some crankcases have sealing closure caps which twist-in, but which are not breather caps. Those devices are not pertinent to the present invention. The present invention comprises a combination of the twist-in feature and the breather feature which combination is thought to be non-existant in the prior art.
Another type of prior-art device, less commonly used, is a screw in type wherein the breather cap has a threaded neck which cooperates with a threaded opening. This is undesirable for a number of reasons, including that the thread can be put in skewed and it requires more time and manipulation than the quarter to half-turn used in the invention cap. It is also more complicated and expensive to manufacture.
The invention also provides an improved manner of assembly and of fabricating the locking fingers required by the twist-in attachment method. This comprises an additional sleeve positioned around the throat portion of the base plate, with the finger portions being formed simultaneously in the throat and sleeve portions such that the part is rigidified and the radial extent of the fingers is increased. This sleeve provides important advantages including reduction of assembly time, reduction of tooling, and the ability to plate the parts of the cap prior to assembly and to thereafter put on sealing means and capture those sealing means in place by forming the locking fingers in the sleeve.